The subject matter disclosed herein relates to controls for turbomachinery systems, such as gas turbines, and more specifically, to systems and methods for improving controls of gas turbine systems having a bottoming cycle system.
Turbomachine systems may include a variety of components and subsystems participating in a process. For example, a turbomachine may include a load, fuel lines, combustors, turbine system, exhaust systems, and so forth, which generate exhaust gases. The exhaust gases generated from the turbomachine system may be fed into a bottoming cycle, such as a heat recovery steam generator (HRSG). An HRSG may convert the exhaust gas to steam, superheat the steam, and feed the steam to a steam turbine. The temperature of the exhaust gas may have an impact on the life of the turbomachine system and the HRSG, and it is dependent on the firing temperature within the turbomachine system.
In a turbomachine system, the firing temperature is the temperature produced within the turbine's combustion system (e.g., flame temperature). Typical turbomachines generally run at a high firing temperature load path because of combustion system limitations and inflexibility. For example, the higher firing temperature is generally utilized to satisfy emissions, lean blow-out, and combustion dynamics requirements. However, higher firing temperature load paths may cause shorter life of a turbomachine system and its combustion parts, as well as a higher turbine exhaust temperature. In turn, higher turbine exhaust temperature leads to higher steam temperature. In order to maintain the steam temperature within the steam turbine and HRSG design temperature limits, water is oftentimes sprayed into superheater and reheater steam circuits. As a result, the HRSG's pressure parts and steam piping's lives are shortened. Further, combined cycle efficiency is lowered. Thus, there is a need to enhance turbomachine system life while reducing the impact on combined cycle efficiency.